V 1.7.1 works fine, but in my case it needed a couple of tweaks to work with a different table prefix (I don't use wp_ ) and to detect "JPEG Support" in GD (the script looks for "JPG Support"). Fixed the first one and got rid of database errors. The second one solves the issue when installing.
Other than that however I am unable to exclude any images from watermarking. I'm sure it's something small and if I knew how to turn on the debugging (which I saw in the code) I could probably find what's preventing it from working as intended.
I'm still giving it 5 stars since it's quite acceptable such as it is :)